The disclosure relates generally to the fabrication of semiconductor bond pad structures, and more particularly, to a structure and method of forming a bond pad structure having enhanced reliability.
Semiconductor bond pad structures having bond wires and solder bump structures using flip chip technology continue to face new challenges as semiconductor device geometries continue to decrease in size. As a consequence of device miniaturization, the RC time constant of the interconnection between active circuit elements increasingly dominates the achievable chip speed-power product. One challenge is the adoption of extreme low-k (ELK) dielectric materials for use in semiconductor bond pad structures to reduce RC delay and parasitic capacitances. ELK dielectric materials generally have dielectric constant (k) values of less than about 2.5. However, as the k values decreases, as a general rule, the strength of the dielectric material decreases and these ELK materials are mechanically much weaker than the conventional silicon dioxide layers. Hence, many ELK materials are highly susceptible to cracking or lack the strength needed to withstand some mechanical processes, such as when the bond pad structure is subjected to an application of force. For example, during wire bonding tests, the overlying bond pad receives a large bonding force causing defect formation or cracking of the underlying inter-metal dielectric (IMD) layers. These wire bonding and other bonding processes induce mechanical and temperature stress in and around the bond pad, including in the conductive and dielectric layers underlying the bond pad.
These cracks may also come about when the device is subjected to thermal cycling during manufacturing, assembly, packaging, testing, and handling. Furthermore, these cracks may propagate as a result of the differences in the coefficients of thermal expansion (CTE) between different semiconductor chip materials. These cracks and peeling of various layers under the bond pad can adversely affect device performance and reliability.
For these reasons and other reasons that will become apparent upon reading the following detailed description, there is a need for an improved bond pad structure and a method of fabrication that avoids the reliability issues associated with conventional bond pad structures. The method should be low cost and use existing manufacturing equipment so that no investment in new equipment is needed.